I once considered the possibility of uploading the entire address book to my servers, too. In fact, I even considered email/sms spamming everyone in those address books with "invitations" from the address book owner to download my app. Of course, I did not end up doing any of that nefarious stuff. Not even uploading the address book for innocent "Add Friends" features. But the fact remains that given the freedom to do so, almost every developer will be, at least, tempted to take advantage of it. Most will.
I honestly don't think Path did anything wrong and I'm sure they kept the information secure on their servers. It's Apple that somehow let this one slip through.